This invention relates to a cathode-ray tube socket and, more particularly, to a cathode-ray tube socket having a connector section for connecting screen lead cables and ground lead cables connected with a substrate having the cathode-ray tube socket mounted thereon.
An example of the prior art cathode-ray tube socket will be described with reference to FIGS. 1 and 2. A cathode-ray tube socket 11 made of electrically insulating material comprises a socket body 12 into which terminal pins of the cathode-ray tube are inserted for connection, and a high-voltage discharge chamber 13 integrally molded with the side of the body. The socket body 12 is generally in the form of a disc plate having a substantial thickness and is formed with a housing portion 15 for accommodating the base (not shown) of the cathode-ray tube having a circular cross-section centered on the central line 14 of the body. The socket body 12 is further formed with a plurality of contact seating sections 17 circumferentially equally spaced apart and annularly arrayed on a circle around the central line 14 and corresponding terminal pin insertion apertures 16 through which the terminal pins are inserted. The contact seating sections 17 are in communication with the corresponding terminal pin insertion apertures 16 and extend rearwardly upto the back face of the cathode-ray tube socket 11. Accommodated in these contact seating sections 17 are low-voltage contacts 18. Formed in the socket body 12 at a position substantially equally spaced from the opposite ends of the circular array of the contact seating sections 17 and the communicating terminal pin insertion apertures 16 and located on the circle common to that on which the contact seating sections 17 are arrayed is a high-voltage contact seating section 17h in which there is accommodated a high-voltage contact 18h for connection with a high-voltage terminal pin of the cathode-ray tube.
In this example, the socket body 12 is formed around its outer periphery with a stepped portion 12S over which there is fitted an exposed grounding conductor 19 in the form of an arcuately bent strip. As shown in FIG. 3, the grounding conductor strip 19 has discharge electrode tongues 19T spaced at equal angular intervals and each formed in its center with a spherical protrusion 19P. There are discharge chambers 21 defined between the middle portions of the terminals of the annularly arrayed contacts 18 and the corresponding discharge electrode tongues 19T of the grounding conductor 19. In each of the discharge chambers 21 there is defined a discharge gap between the spherical protrusions 19P each of the discharge electrode tongues 19T of the grounding conductor 19 and the middle portion of the terminal 18T of the contact 18.
Referring to FIGS. 1, 2, 4 and 5, the high-voltage discharge chamber 13 is defined by a generally rectangular housing 42 integrally formed with the side of the socket body 12 adjoining the high-voltage contact seating section 17h, and a rectangular cover 43 closing the top opening of the rectangular housing 42. Disposed in the high-voltage discharge chamber 13 is a pair of high-voltage discharge electrodes 31 and 32 spaced apart to define a high-voltage discharge gap therebetween. The high-voltage contact 18h and the high-voltage discharge electrode 31 are interconnected by means of a connecting conductor 33 (FIGS. 1, 2 and 5). The high-voltage discharge electrode 31 is semi-spherical in shape and has a rectangular flange-like fixing plate 35 integrally formed therearound. The fixing plate 35 is fitted in a slit 71 formed in a high-voltage discharge electrode retaining wall 70 (FIG. 4) provided in the interior of the high-voltage discharge chamber 13 to hold the high-voltage discharge electrode 31 in place in the high-voltage discharge chamber 13. The other high-voltage discharge electrode 32 is likewise semi-spherical and has a rectangular mounting flange 36 integrally formed therearound. The mounting flange 36 is also held in the high-voltage discharge chamber 13. The convex surfaces of the high-voltage discharge electrodes 31 and 32 are in opposing relation to each other to define a high-voltage discharge gap therebetween. The cover 43 has U-shaped integral engaging portions 61 depending from the opposite side walls thereof and adapted to snap into engagement with locking engagement protuberances 62 formed on the opposite side walls of the housing 42 when the cover 43 is fitted over the housing 42 to close the open top of the housing 42.
As shown in FIG. 4, the high-voltage discharge electrode 31 has a lead cable pinching chamber 41 formed in the back face thereof. A connecting portion 38 extends from one side edge of the fixing plate 35 of the high-voltage discharge electrode 31 perpendicularly into the lead cable pinching chamber 41 in which the connecting portion 38 extends upwardly to form a receiving plate 39 in spaced and opposing relation to the fixing plate 35. The receiving plate 39 is bent downwardly obliquely at an acute angle o to form a contact tab 37 which defines between the contact tab and the fixing plate 35 a gap narrowing progressively as the tab extends downwardly. The fixing plate 35 and the contact tab 37 thus defines a lead cable pinching member 30, and a lead cable insertion aperture 48 is formed through the cover 43 for guide the leading end of a lead wire or cable toward the gap of the lead cable pinching member 30 with a tubular projection 49 concentric with and surrounding the lead cable insertion aperture 48 and extending integrally upwardly from the top surface of the cover 43. The top wall, that is, the cover 43 of the lead cable pinching chamber 41 is formed adjacent the tubular projection 49 with a slot 52 communicating with the lead cable pinching chamber 41.
The lead cable insertion aperture 48 is located in proximity to and in opposition to the distal end of the contact tab 37 so that the core of the high-voltage focusing lead cable G3 which is an external lead cable may be inserted through the insertion aperture 48 into the lead cable pinching chamber 41 to resiliently hold the leading end of the core between the fixing plate 35 and the contact tab 37 of the lead cable pinching member 30. The inner diameter of the tubular projection 49 surrounding the periphery of the lead cable insertion aperture 48 is made approximately equal to the outer diameter of the insulation coating of the lead cable G3 so as to act as a guide for the high-voltage focusing lead cable G3 as it is inserted into the chamber 41 as well as to snugly embrace the insulation coating of the lead cable to thereby prevent vibration thereof.
A generally rectangular swing plate 53 is connected integrally with the side of the socket body 12 opposite from the cover 43 by means of a hinge 54 (FIGS. 1 and 2) formed integrally with the side of the socket body. The swing plate 53 has a retaining tab 51 formed integrally with and bent at a right angle to the plate 53 so that the tab 51 may be rotated into the housing 42 through the slot 52 formed in the cover 43 as the swing plate 53 is pivoted about the hinge 54. When the swing plate 53 is pivoted down against the top surface of the cover 43, a U-shaped engaging portion 57 (FIG. 2) depending from one side edge of the swing plate 53 is brought into snapping engagement with an engagement protuberance 56 extending from one side wall of the cover 43 to secure the plate to the cover. With the high-voltage focusing lead cable G3 inserted through the lead cable insertion aperture 48 into between the fixing plate 35 and the contact tab 37, upon the swing plate 53 being pivoted to press down the top surface of the cover 43 as stated above, the receiving plate 39 is subjected on its side face to a lateral force from the retaining tab 51 to be resiliently urged toward the fixing plate 35 as shown in FIG. 4. As a result, the lead cable pinching member 30 may be locked in place with the focusing lead cable G3 pinched between the fixing plate 35 and the contact tab 37 with an increased pressure. In addition, the contact tab 37 has its forward end oriented to present a sharp edge in a direction opposite to the direction of withdrawal of the lead cable to thereby act as a stop to prevent dislodgement of the lead cable. It is thus to be understood that this arrangement insures positive electrical and mechanical connection of the focusing lead cable G3 with little possibility of dislodgement.
The fixing plate 35, the contact tab 37, the slot 52, the insertion aperture 48, the tubular projection 49, the retaining tab 51, the swing plate 53 and the hinge 54 shown in FIG. 4 constitutes a high-voltage lead cable connector section 200. When it is desired to withdraw the high-voltage focusing lead cable G3 from the high-voltage lead cable connector section 200, it is only required to turn the swing plate 53 to dislodge the retaining tab 51 from the slot 52 to thereby unlock the lead cable pinching member 30. This type of connector section 200 is called lead cable quick-connection type because locking and unlocking of the lead cable pinching member 30 may be readily effected. The cathode-ray tube socket as described above is disclosed in U.S. Pat. No. 4,822,301, for example.
The cathode-ray tube socket 11 is mounted on the surface of a printed-circuit board 100 for a cathode-ray tube, for example as shown schematically in FIG. 6, and the terminals 18T (see FIGS. 1 and 2) of some preselected ones of the contacts 18 are passed through terminal holes 110 formed through the printed-circuit board 100 as shown schematically in broken lines and soldered to the printed wiring in the back surface of the board through which printed wiring the terminals are electrically connected with a board-in connector 108 and a connector pin 103 mounted on the top surface of the board. The cathode-ray tube has its terminal pins inserted into the terminal-pin insertion apertures 16 of the cathode-ray tube socket 11 to be contact connected with the contacts 18 accommodated in the apertures 16. In addition, the high-voltage lead cables G2 and G3 extending from a flyback transformer, not shown are coupled to the connector pin 103 and the tubular projection 49, respectively. The lead cable G3 is a high-voltage focusing lead cable for supplying focusing voltage in the order of 10 kV from the flyback transformer. The cable G2 is a screening lead cable for supplying screening voltage in the order of 1 kV from the flyback transformer. Connected to the board-in connector 108 are a lead cable G1, a cathode lead cable 4C and a heater lead cable 4H extending from a main board (not shown). While only three lead cables are illustrated here, actually about seven lead cables including other lead cables from the main board are connected to the connector 108 and then connected through the printed circuit of the printed-circuit board 100 with the corresponding terminals of the cathode-ray tube socket 11 to provide relatively low voltage in the order less than 100 V.
The terminal of an anode cable 4A from the flyback transformer is connected by hand directly to an anode terminal, not shown, of the cathode-ray tube to provide an anode voltage in the order of 30 kV. Terminal holes 105, 106 are used to connect individual components such as resistances, capacitors and the like. Although not shown, a grounding lead cable besides the lead cable G2 may also be connected to the printed-circuit board 100 of the cathode-ray tube to lead the grounding terminal pin of the cathode-ray tube socket to the main board or the frame of the associated apparatus.
Heretofore, the screening lead cable G2 has been connected to the cathode-ray tube printed-circuit board 100 by preliminarily securedly soldering the connector pin 103 protruding from the top surface of the printed-circuit board 100 through a G2 insertion hole 102 formed through the board to the printed circuit formed in the back surface of the printed-circuit board 100, and fitting the crimp terminal 104 attached to the distal end of the screening lead cable G2 over the connector pin 103 protruding from the board. Alternatively, instead of providing the connector pin 103, the connection of the lead cable G2 has been effected by introducing the distal end of the core of the lead cable G2 from the top surface of the printed-circuit board 100 through the G2 insertion hole 102 formed through the board to the back surface of the board and connecting the distal end of the core directly to the printed circuit in the back surface of the board by hand-soldering. As shown in broken lines in FIG. 6, the lead cables G1 and G2, the cathode lead cable 4C and the heater lead cable 4H are connected with the corresponding terminals 18T and hence the corresponding contacts 18 of the cathode-ray tube socket 11 through the printed circuit in the back surface of the board 100.
In this regard, it should be noted that despite the fact that most of the surface mounted components on the cathode-ray tube printed-circuit board 100 are dip-soldered to the board, the connection of the lead cable G2 is made by hand-soldering to the cathode-ray tube printed-circuit board 100 separately from those components, which is undesirable from the viewpoint of efficiency in the connecting operation. In contrast, in the case that the connection of the lead cable G2 is made by means of the connector pin 103 provided on the cathode-ray tube printed-circuit board 100, it is required to attach the crimp terminal 104 on the side of the screening lead cable G2. The need for the operation of pressure attaching the climp terminal 104 to the screening lead cable G2 also adds to the complexity of the connecting operation. When the grounding lead cable from the main board (not shown) is connected to the earthing pin of the cathode-ray tube, it has been a common practice to connect the grounding lead cable directly to the terminal 18T corresponding to the earthing pin.
As discussed above, the conventional cathode-ray tube socket known as the lead cable quick-connection type was configured to provide for connection to the socket without the need for soldering with respect to the focusing lead cable G3, but still required the use of soldering or the aforesaid climp terminal and pin for connection of the screening lead cable G2 or the grounding lead cable (see the Japanese Patent Application Publication Kokai No. 9-50837).
A high voltage is applied to the screening lead cable G2. In view of this, when the screening lead cable G2 is connected to the corresponding terminal of the cathode-ray tube socket through the printed wiring of the printed-circuit board 100 to which the cathode-ray tube socket is mounted, it is required to make provision for preventing deleterious influences such as electrical leakage from being exerted on the terminals of electrical components inserted in the terminal holes 105, 106 adjacent the G2 insertion hole 102, the printed wiring adjacent the printed wiring extending from the G2 insertion hole 102 up to the terminal hole 110b for the corresponding socket terminal, and the socket terminals inserted in the terminal holes 110a and 110c adjacent said corresponding socket terminal, and others. To this end, there are formed in the printed-circuit board two slits 101 extending from locations intermediate the G2 insertion hole 102 and the terminal holes 110a and 110c to locations intermediate the terminal hole 110b associated with the G2 insertion hole 102 and the terminal holes 110a and 110c adjacent the terminal hole 110b. However, if the printed-circuit board is miniaturized with increased packaging density in order to accommodate miniaturization of the entire apparatus, there would be no room for providing the slits 101.
In addition, the quick-connection type connector disclosed in the aforesaid Japanese Patent Application Publication Kokai No. 9-50837 is mechanically separate from the socket body, requiring a correspondingly increased number of parts and hence additional steps of operation for assembling and connecting the quick-connection type connector.